1. Field of the Invention
The present invention relates to a semiconductor device including an antifuse and a manufacturing method thereof.
Note that the semiconductor device in this specification refers to all devices that can function by utilizing semiconductor characteristics, and electro-optic devices, semiconductor circuits, and electronic appliances are all semiconductor devices.
2. Description of the Related Art
A ROM (read only memory), which performs only reading, is classified into a mask ROM and a PROM (programmable ROM). A fuse ROM and an antifuse ROM are a kind of PROM. The mask ROM is a ROM to which information is written using a photomask in a manufacturing process. The fuse ROM is a ROM in which a fuse that is in a conductive state in a manufacturing process is used as a memory element and information is written in such a manner that the fuse is disconnected by current flowing after the manufacture. On the other hand, the antifuse ROM is a ROM in which an antifuse that is in a non-conductive state in a manufacturing process is used as a memory element and information is written in such a manner that the antifuse is short-circuited by current flowing after the manufacture.
In Patent Document 1, an antifuse in which amorphous silicon is interposed between a pair of conductors is described. One of electrodes is formed of metal, and the amorphous silicon and the metal are made to react with each other to form silicide, whereby the antifuse is placed in a conductive state.
In Patent Document 2, an antifuse having a structure in which an amorphous silicon film containing germanium is interposed between wirings is described. The proportion of germanium in the amorphous silicon film is adjusted and the crystallization temperature of the amorphous silicon film is decreased, whereby writing voltage can be lowered.
In Patent Document 3, an antifuse formed using a stacked body of an electrode, silicon nitride, amorphous silicon, silicon nitride, an electrode, and the like is described.